1. Field of the Invention
The present invention relates generally to power lawnmowers and, more particularly, to power lawnmowers which employ cutting blades made of filaments.
3. Description of the Prior Art
The use of power lawnmowers that employ filaments for cutting blades is well known in the art. In this respect, throughout the years, a number of innovations have been developed relating to filament based cutting blades for lawnmowers, and the following U. S. patents are representative of some of those innovations: U.S. Pat. Nos. 4,112,653, 4,201,034, 4,726,176, 4,819,416, and 5,713,191. More specifically, U.S. Pat. No. 4,112,653 discloses a filament cutting blade for a lawnmower that is retained on a support disc by centrifugal force on the disc as the disc spins. Because the degree of centrifugal force varies with the rate of spin of the disc, it would be desirable if filaments were secured to a support disc in a manner which does not rely upon the use of centrifugal force on the disc.
U.S. Pat. No. 4,201,034 discloses a lawnmower that employs plural reels of filaments. Because of their complexity and their weight, it would be desirable if a lawnmower employed filaments without employing plural reels of filaments supported on a disc.
U.S. Pat. No. 4,726,176 discloses a lawnmower that has a disc that has horizontal grooves for receiving filaments. Once grooves are machined into a filament retaining disc, there is a substantial risk that the disc will be out of balance when it spins. Therefore, to avoid this risk, it would be desirable if a filament employing lawnmower were provided that does not employ a disc that has horizontal grooves machined into the disc for retaining the filaments.
U.S. Pat. No. 4,819,416 discloses a lawnmower that employs filaments attached to a disc that has pairs of adjacent vertical channels separated by a common wall. A filament is threaded in through one channel, around the common wall, and out through the second channel. With this device, two vertical channels are required for each filament that is employed. Also, the filament must be threaded into and out from the two vertical channels. To avoid the duplication, it would be desirable if a lawnmower that employs filaments were provided that does not employ two vertical channels for each filament that is employed. In addition, it would be desirable if a filament-employing lawnmower were provided that does not require a filament to be threaded into and out from a supporting disc.
U.S. Pat. No. 5,713,191, in a manner similar to above-mentioned U.S. Pat. No. 4,819,416, discloses a lawnmower disc that supports filaments by having the filaments threaded through pairs of adjacent vertical channels in the disc.
Still other features would be desirable in a filament employing lawnmower blade apparatus. For example, rather than having pairs of adjacent vertical channels for supporting a single filament in a disc, it would be desirable if a lawnmower disc had only one vertical disc channel for supporting each filament. In addition, rather than machining a lawnmower disc in a complex way to receive a filament, it would be desirable if the lawnmower disc were machined simply to receive a fastener, and the fastener is provided with a filament receiving channel.
Thus, while the foregoing body of prior art indicates it to be well known to use lawniowers that employ filaments for cutting blades, the prior art described above does not teach or suggest a filament employing lawnmower blade apparatus which has the following combination of desirable features: (1) has filaments secured to a support disc in a manner which does not rely upon the use of centrifugal force on the disc; (2) employs filaments without employing plural reels of filaments supported on a disc; (3) dies not employ a disc that has horizontal grooves machined into the disc for retaining the filaments; (4) does not employ two vertical channels for each filament that is employed; (5) does not require a filament to be threaded into and out from a supporting disc; (6) has only one vertical disc channel for supporting each filament; and (7) has a lawnmower disc that is machined simply to receive a fastener, and the fastener is provided with a filament receiving channel. The foregoing desired characteristics are provided by the unique filament employing lawnmower blade apparatus of the present 20 invention as will be made apparent from the following description thereof. Other advantages of the present invention over the prior art also will be rendered evident.